Kiln wash

I am currently working with glasses (technically glass composites) as a nuclear material and I have some powder which i want to take to 1300 degrees, past the melting point. Ive tried this several times but they all stuck to the crucible i was using. With a bit of looking around the net i came across the use of a kiln wash, which is what i think i shouldve done to prevent this, a little bit more research left me with a 50:50 recipe of kaolin to alumina hryrdrate, however I dont know enough about this to know whether it would partially bond (physically or otherwise) to the glass. For good results it cant bond at all. I was hoping someone here knows if there is a way i can prevent my samples from sticking to the crucible, or specfic recipes that i could use if a kiln wash is the way to go. Any thoughts would be greatly appreciated.

I am currently working with glasses (technically glass composites) as a nuclear material and I have some powder which i want to take to 1300 degrees, past the melting point. Ive tried this several times but they all stuck to the crucible i was using. With a bit of looking around the net i came across the use of a kiln wash, which is what i think i shouldve done to prevent this, a little bit more research left me with a 50:50 recipe of kaolin to alumina hryrdrate, however I dont know enough about this to know whether it would partially bond (physically or otherwise) to the glass. For good results it cant bond at all. I was hoping someone here knows if there is a way i can prevent my samples from sticking to the crucible, or specfic recipes that i could use if a kiln wash is the way to go. Any thoughts would be greatly appreciated.

Many thanks!

kiln was will bond partially to your glass. What type of crucible are you using? It sounds like some kind of refractory ceramic material. If its a small crucible, you might think of using graphite instead. Also, if possible, could a moderator move this to technical?

I have been doing some experimenting with crushed bottle glass and frits and have used kiln wash as a separator, the wash has been sticking to the melted glass. When I played with glass 30 years ago I bought a glass separator powder from a glass firing supplier. I think I'm going to try some of it again, at the time I thought it was just kiln wash, hopefully someone on this forum will come up with a better idea.

kiln was will bond partially to your glass. What type of crucible are you using? It sounds like some kind of refractory ceramic material. If its a small crucible, you might think of using graphite instead. Also, if possible, could a moderator move this to technical?

Its a thermal gravimetric analysis type crucible so it's about 20ml in capacity and although I dont know for sure, I think it's an alumina crucible. I think I can get my hand on a graphite crucible, but my head would be wanted on a plate by the guy who owns them, if it stuck. Is there any chance this could happen?

I've never had graphite stick to hot glass... But that's not to say that it couldn't I suppose... Getting one to test with shouldn't be expensive--a quick search for "graphite crucible" on ebay yields a bunch of results that might be suitable. I have seen that glass separator stuff the the previous poster mentioned, and I have seen that stuff stick as well--not sure what its made of, but its definitely not your standard kiln wash.

I have a family member who makes glass marbles. He also makes graphite molds that marble artists use to spin the melted glass marbles in to round them. For more info about those, click here.. If you want to talk with him and cannot find him online, you are welcome to email me. He might be able to give you a definitive answer.

@Diane Puckett That sound like a good idea, im finding that a big problem with academic work is the lack of of hands-on-work and the experience that goes with it. Next best thing from getting that experience is talking to someone already with it.

@justanassembler I managed to get my hands on a graphite crucible and im going to try it without the seperator. I saw the stuff you were talking about online and hopefully there is a college registered site i can buy it off. Biggest problem im having is the places im actually allowed to buy this stuff from.

I am currently working with glasses (technically glass composites) as a nuclear material and I have some powder which i want to take to 1300 degrees, past the melting point. Ive tried this several times but they all stuck to the crucible i was using. With a bit of looking around the net i came across the use of a kiln wash, which is what i think i shouldve done to prevent this, a little bit more research left me with a 50:50 recipe of kaolin to alumina hryrdrate, however I dont know enough about this to know whether it would partially bond (physically or otherwise) to the glass. For good results it cant bond at all. I was hoping someone here knows if there is a way i can prevent my samples from sticking to the crucible, or specfic recipes that i could use if a kiln wash is the way to go. Any thoughts would be greatly appreciated.

Several great books out there on cast glass. Buy one and work with molds that you can crumble off your work. Using a flower pot on top you can slowly add cullet or powders that will melt into the mld. It is a bit complicated and there are great classes at the Appalachian Center for Crafts, Penland and of course the best place to eat and learn Haystack.

STEPHEN ROBISON
Head of Ceramics, Central Washington University
Ellensburg WA